Layered lithospheric mantle in the central Baltic Shield from surface waves and xenolith analysis

Bruneton, Marianne; Pedersen, Helle A.; Vacher, Pierre; Kukkonen, Ilmo; Arndt, Nicholas; Funke, Sigward; Friederich, Wolfgang; Farra, Véronique

doi:10.1016/j.epsl.2004.07.034

Cited by 56 publications

(61 citation statements)

References 34 publications

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“…Jun Korenaga is thanked for providing a preprint of a paper containing new analyses of olivine creep parameters. (Li and Burke, 2006) > 150 km (Chen et al, 2007) Consistent with 250 km (Bruneton et al, 2004a) S-Receiver function~ 250-300 km (Kumar et al, 2007) Magnetotelluric (MT) 230 km (Miensopust et al, 2006) 210 km at LdG 260 km average (Jones et al, 2003) 205 km at NAT (Jones, 1999) > 300 km (Korja, 2007) . The LAB may also correlate with a downward extinction of seismic anisotropy (e.g., Gaherty and Jordan, 1995) or a change in the direction of anisotropy (e.g., Debayle and Kennett, 2000a;2000b;Sebai et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

“…The electrical LAB is marked by a significant reduction in electrical resistivity. Bruneton et al, 2004a) and MT (BEAR; Engels et al 2002) experiments. KK denotes Kuopio-Kaavi kimberlites.…”

Section: Discussionmentioning

confidence: 99%

“…The presence of a low-velocity zone beneath the high-velocity lid can be taken as an indication of the LAB (e.g., Bruneton et al, 2004a;Pontevivo and Thybo, 2006), though the depth range of the boundary region will depend on the model parameterization. Proxies for the LAB are given by many authors, based on a number of different criteria that stem from surfacewave observations:…”

Section: Defining the Lab Using Surface-wave Observationsmentioning

confidence: 99%

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The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons

Eaton

Darbyshire

Evans

et al. 2009

Lithos

393

288

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The lithosphere-asthenosphere boundary (LAB) is a first-order structural discontinuity that accommodates differential motion between tectonic plates and the underlying mantle. Although it is the most extensive type of plate boundary on the planet, its definitive detection, especially beneath cratons, is proving elusive. Different proxies are used to demarcate the LAB, depending on the nature of the measurement. Here we compare interpretations of the LAB beneath three The seismic LAB beneath cratons is typically regarded as the base of a high-velocity mantle lid, although some workers infer its location based on a distinct change in seismic anisotropy.Surface-wave inversion studies provide depth-constrained velocity models, but are relatively insensitive to the sharpness of the LAB. The S-receiver function method is a promising new seismic technique with complementary characteristics to surface-wave studies, since it is 2 sensitive to sharpness of the LAB but requires independent velocity information for accurate depth estimation. Magnetotelluric (MT) observations have, for many decades, imaged an "electrical asthenosphere" layer at depths beneath the continents consistent with seismic lowvelocity zones. This feature is most easily explained by the presence of a small amount of water in the asthenosphere, possibly inducing partial melt. Depth estimates based on various proxies considered here are similar, lending confidence that existing geophysical tools are effective for mapping the LAB beneath cratons.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Defining the Lab Using Surface-wave Observationsmentioning

confidence: 99%

See 1 more Smart Citation

The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons

Eaton

Darbyshire

Evans

et al. 2009

Lithos

393

288

View full text Add to dashboard Cite

show abstract

“…In any case, all the methods that take into account propagation effects outside an array should be parametrized to allow for large deviations from the great-circle. In previous 3-D imaging (Bruneton et al 2004;Salaün et al 2012) we observed that the single main parameter that improved fit to data was the propagation direction, and that curvatures in the wave front remained a secondary effect.…”

Section: O N C L U S I O N S a N D Discussionmentioning

confidence: 99%

“…Beamforming has also been used in lithospheric imaging to obtain the average phase velocities beneath an array of many seismic stations. Such techniques were for example applied in the Baltic Shield by Bruneton et al (2004), Maupin (2011) and Pedersen et al (2013). In these studies, the estimated backazimuth is a side product, as the phase velocity and propagation direction are estimated simultaneously (e.g.…”

Section: Introductionmentioning

confidence: 99%

Arrival angle anomalies of Rayleigh waves observed at a broadband array: a systematic study based on earthquake data, full waveform simulations and noise correlations

et al. 2015

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S U M M A R YDeviation of seismic surface waves from the great-circle between source and receiver is illustrated by the anomalies in the arrival angle, that is the difference between the observed backazimuth of the incident waves and the great-circle. Such arrival angle anomalies have been known for decades, but observations remain scattered. We present a systematic study of arrival angle anomalies of fundamental mode Rayleigh waves (20-100 s period interval) from 289 earthquakes and recorded by a broadband network LAPNET, located in northern Finland. These observations are compared with those of full waveform synthetic seismograms for the same events, calculated in a 3-D Earth and also compared with those of seismograms obtained by ambient noise correlation. The arrival angle anomalies for individual events are complex, and have significant variations with period. On average, the mean absolute deviation decreases from ∼9 • at 20 s period to ∼3 • at 100 s period. The synthetic seismograms show the same evolution, albeit with somewhat smaller deviations. While the arrival angle anomalies are fairly well simulated at long periods, the deviations at short periods are very poorly modelled, demonstrating the importance of the continuous improvement of global crustal models. At 20-30 s period, both event data and numerical simulations have strong multipathing, and relative amplitude changes between different waves will induced differences in deviations between very closely located events. The source mechanism has only limited influence on the deviations, demonstrating that they are directly linked to propagation effects, including near-field effects in the source area. This observation is confirmed by the comparison with seismic noise correlation records, that is where the surface waves correspond to those emitted by a point source at the surface, as the two types of observations are remarkably similar in the cases where earthquakes are located close to seismic stations. This agreement additionally confirms that the noise correlations capture the complex surface wave propagation.

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Constraints on shear velocity in the cratonic upper mantle from Rayleigh wave phase velocity

Hirsch

Dalton

Ritsema

2015

Geochem Geophys Geosyst

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The standard model of the thermal and chemical structure of cratons has been scrutinized in recent years as additional data have been collected. Recent seismological and petrological studies indicate that the notion of cratonic lithosphere as a thick thermal boundary layer with a very depleted and dehydrated composition may be overly simplified and does not explain all aspects of the seismological and petrological observations. We designed a simple forward-modeling experiment to identify a suite of one-dimensional shear-velocity profiles that are representative of the cratonic upper mantle. The mean and standard deviation of phase velocities for Rayleigh waves that travel paths primarily over cratons were calculated from a global data set in the period range 40 to 300 seconds. One-dimensional Earth models were calculated using two approaches, and the predicted Rayleigh wave phase velocity for each model was compared to the observed range to identify models that provide a satisfactory fit to the observations. With the first approach, shear velocity was predicted from cratonic geotherms that were calculated for a range of surface heat-flow and crustal-thickness values. With the second approach, profiles of shear velocity were generated using random perturbations to 1-D global Earth model STW105. In total 26250 geothermv generated and 80,000 randomly generated 1-D Earth models were generated for comparison to the observations. The results show that cratonic shear velocity is higher than STW105 to depths greater than 200 km. The majority of randomly generated models contain increasing velocity with depth to 250-300 km while the majority of geotherm-generated models contain a low velocity layer in the depth range 100-150 km.vi

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Layered lithospheric mantle in the central Baltic Shield from surface waves and xenolith analysis

Cited by 56 publications

References 34 publications

The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons

The elusive lithosphere–asthenosphere boundary (LAB) beneath cratons

Arrival angle anomalies of Rayleigh waves observed at a broadband array: a systematic study based on earthquake data, full waveform simulations and noise correlations

Constraints on shear velocity in the cratonic upper mantle from Rayleigh wave phase velocity

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